The disclosure is directed to rotating structures where monitoring the structure status can improve reliability and reduce down-time and maintenance cost. The disclosure is directed particularly to structures that generate energy from the flow of gases or liquids, such as wind turbines. The disclosed technology can be applied to other rotating members that may need to be monitored such as aircraft propeller blades and turbine fan blades, or centrifuge arms. The disclosed technology can also be applied to non-rotating structures or bodies under stress or load such as a tall building or the mast of a boat.
Wind turbines form an important part of a balanced energy strategy. Many wind turbine blades are made by hand out of fiberglass. If not properly manufactured, after few months of operation they may begin to develop cracks at weak spots in the blade. These cracks are initially small, and if detected can be repaired on site with little cost, with the blade still mounted on the turbine. If the crack is not repaired promptly, the crack becomes larger until the blade ultimately fails (e.g., breaks). Once a blade fails, the turbine must be taken out of service, until a new blade can be transported to the site and installed, which is very expensive. Prompt detection of turbine blade cracks is therefore important for economical operation of wind turbine energy facilities.
Blade balance is also very important when operating wind turbines. Typically on each turbine there are multiple (e.g., three) blades, which should be balanced prior to installation to prevent any excessive unwanted loads or forces on the main shaft and the gearbox. Damage to the gearbox due to blade imbalance is gradual and will result in excessive gearbox wear within a few months of operation. Wind turbulence and turbine yaw also will have an adverse effect on the gearbox. Blade imbalance can also occur due to local weather conditions, for example due to imbalanced ice or snow accumulation on one or more blades. As turbine down time and gearbox repair is very expensive, early detection of blade imbalance and the application of corrective action to balance the blades are important to prevent problems with the wind turbine.
Lightning strikes also form a hazard for wind turbine blades, and detection of lightning strikes also allows for more efficient and cost-effective turbine blade maintenance. Shock to turbine blades, for example from striking an errant bird, wind-borne debris, and so on are also a risk.
Early identification of risks such as blade imbalance, lightning strikes, and mechanical shocks is crucial to safe, efficient, and cost-effective operation. However, blades rotate around a pivot point, which makes it difficult to provide power to a sensor and receive sensor signals over a wired connection. Effective monitoring of the turbine blades should sense strain on the rotating turbine blades, synchronize measurements with the blade rotation to account for strain effects due to gravitational forces, send data wirelessly to a central location for analysis, and provide a means to remotely power the sensor. Such a monitoring system has not been disclosed in the prior art.